1. Field of the Invention
The present invention relates to a method of recognizing color bars on double-sided color prints, a color print quality control system and a color print quality evaluation apparatus.
2. Related Art
A single-sided color print with its single side printed in color is produced by printing a color print image on a single side of a substrate with using plural basic different colors such as cyan (C), magenta (M), yellow (Y) and black (Bk). A double-sided color print with its both sides printed in color is produced by additionally printing a color print image on another side of the substrate in the same manner as in the single-sided color printing.
In either case, whether the single-sided color printing or the double-sided color printing is carried out, a color print image printed on each substrate is subjected to print quality control (e.g., color matching) in order to keep an appropriate quality color print image.
In more detail, according to the print quality control operation (e.g., color matching) for color print images of a color print printed by a single-sided color printing press and a double-sided color printing press, when printing a color print image, a color bar comprised of control patch groups each comprised of plural control patches of plural colors aligned in a given direction, which colors corresponding to basic colors of the color print image, is printed in a certain region or generally a margin of the print where no color print image is printed so as to provide for print quality evaluation. The color bar thus printed is scanned by a color print quality evaluation apparatus (e.g., an apparatus equipped with densitometer and spectrophotometer) so as to detect the print quality (e.g., density) of the control patches of each patch group in the color bar. The print quality control operation in each printing press is thus controlled based on the detected value and its reference value fed back to the printing press. Once receiving the fed back values, each color printing press adjusts the amounts of inks set by ink fountains each including ink fountain keys mounted respectively corresponding to the control patch groups, based on the information representative of the print quality (hereinafter referred simply to print quality information) of the patches in each patch group.
In the above quality control operation, while the feeding back of only the print quality information of a color print image of the single side of a substrate is enough for the single-sided color printing, it is necessary in the double-sided color printing to make the double-sided color printing press recognize that a detected or evaluated color bar is the one printed on a first or second side of the substrate before feeding back of the print quality information.
In the print quality control operation hitherto made for a color print image on each side of a print, an operator needs to check whether an evaluated color bar is the one printed on a first or second side of a double-sided color print every time the evaluation of the print quality is performed based on the control patches of the color bar scanned by a color print quality evaluation apparatus, and send or set this information to the printing press, thus allowing the printing operation of the printing press to be controlled based on the information fed back thereto. In summary, this conventional print quality control operation requires the operator to check whether an evaluated color bar is the one printed on a first or second side of a double-sided color print and send or set this information to the printing press every time the scanning and evaluation are made. This quality checking increases the workload of the operator and hence increases the possibility to cause him to send or set incorrect information to the printing press. Accordingly, the correct print quality information may not be securely fed back to the printing press, making prints unusable as products or causing a lot of time for correction of the feed-back information to the printing press.
In order to address the above problem, a print quality control method as proposed in Japanese Patent Application Laid-open No. Sho-58-214822 employs a double-sided color print with the control patches of a color bar respectively corresponding to plural basic different colors of a color print image, some of them being printed on the first side of the print while the residual being printed on the second side of the print. According to this method, of the control patches of the color bar respectively corresponding to the plural basic colors of the color print image, the patches on the first side and the patches on the second sides of the print are printed respectively in different orientations so as to allow the color print quality evaluation apparatus to detect whether the evaluated control patches are those printed on the first or second side of the print.
In the above method, where the control patches of the color bar printed on the first and second sides of a print in different orientations are respectively printed by different printing sections, the print quality for all the basic colors of the color print images respective printed on the first and second sides of the double-sided color print is hard to be controlled.
Another problem arises when the above method is carried out by a conventional print quality control system, the detailed description of which will be made hereinafter.
For achieving the print quality control operation by carrying out the above method in a conventional color print quality control system, the system is equipped with a color printing press and a color print quality evaluation apparatus. The color printing press is to print, on at least one of the opposite sides of each substrate transferred in a given transfer direction, a color print image composed of plural basic different colors by, for example, ink fountains of plural basic different colors, each including 1st to Mth (M is an integer of 2 or larger) ink fountain keys respectively aligned crossing substantially at a right angle to the substrate transfer direction, and a color bar for evaluation of each of the plural basic different colors of the color print image, which color bar comprised of 1st to Mth control patches aligned respectively corresponding to the 1st to Mth ink fountain keys. The color print quality evaluation apparatus is to scan the 1st to Mth patches of each color print printed by the printing press in a given scanning direction and evaluate the print quality of each patch. The print quality information of each patch evaluated by the color print quality evaluation apparatus is transmitted to the printing press in the order in which the patches are scanned in the given scanning direction so that the amounts of inks set by the 1st to Mth ink fountain keys of the printing press are respectively adjusted based on the print quality information in the order in which they are transmitted from the color print quality evaluation apparatus.
In the thus arranged color print quality control system, each color bar arranged corresponding in position to the aligned ink fountain keys is printed in an uppermost region (hereinafter referred to a leading end region) or lowermost region (hereinafter referred to a trailing end region) in each substrate in the transfer direction, depending on the type or kind of a print. FIG. 10A illustrates a print Q′ with a color bar E printed in the leading end region and FIG. 10B illustrates the print Q′ with the color bar E printed in the trailing end region, which color bar being comprised of 1st to Mth patches D aligned in a direction represented by arrow H crossing substantially at a right angle to the substrate transfer direction represented by arrow G.
In a case where the color bar E is printed in the leading end region of the print Q′, as illustrated in FIG. 10A, a print image IM of the print Q′ is printed upstream to the color bar E in the transfer direction G (an upper part in the Figure). In a case where the color bar E is printed in the trailing end region of the print Q′, as illustrated in FIG. 10B, the print image IM is printed downstream to the color bar E in the transfer direction G (a lower part in the Figure). The color bar E thus printed is scanned by a scanning section J of the color print quality evaluation apparatus in a given scanning direction represented by arrow F. When an image capturing part J1 is located in the scanning section J downward in FIG. 10A, the scanning section J is likely to contact the print image IM printed upward in FIG. 10A and hence stain the print image IM just after printed. In order to address this problem associated with the case where the image capturing part J1 is located in the scanning section J downward in the Figure and the print image IM is printed on the print upward to the color bar E in the Figure, or the image capturing part J1 is located in the scanning section J upward in the Figure and the print image IM is printed on the print downward to the color bar E in the Figure, the print is turned 180° horizontally and then scanned, thereby preventing the scanning section J from contacting the print image IM. FIG. 11A illustrates an operational state where the print Q′ of FIG. 10A is turned 180° horizontally and then scanned by the scanning section J with the image capturing part J1 located downward in the Figure. FIG. 11B illustrates an operational state where the print Q′ of FIG. 10B is scanned by the scanning section J with the image capturing part J1 located downward in the Figure.
The scanning upon turn of the print Q′ by 180° can prevent the scanning section J from contacting the print image IM, but pauses another problem. That is, the scanning section J scans the patches D of the turned print in the order from the Mth patch to the 1st patch in the given scanning direction F (see FIG. 11A), and the print quality information is accordingly transmitted in this order. This causes the amounts of inks set by the 1st to Mth ink fountain keys to be adjusted based on the print quality information transmitted in this reversed order as mentioned above, and hence makes it impossible to control the ink fountain keys based on the correct compensation data. In order to address this problem, a so-called 180-degree turn switch is provided to send to the color print quality evaluation apparatus the information that the print Q′ has been turned 180°. The operator presses this 180-degree turn switch to send to the evaluation apparatus the information that the print Q′ has been turned 180°, thereby allowing the evaluation apparatus to receive the print quality information of the patches D in the order reversed to the order in which the patches are scanned in the given scanning direction F. Thus, the ink fountain keys are adjusted based on the correct compensation data.
According to the above arrangement, the switch must be pressed by the operator to send the information that the print Q′ has been turned 180° to the color print quality evaluation apparatus. This makes the operator's print quality control operation troublesome in the same manner as the above-mentioned print quality control operation. Also, this arrangement is disadvantageous in the fact that once the operator has unintentionally skipped to press the switch, the ink fountain keys cannot be controlled based on the correct compensation data.
It is an object of the present invention to provide a method of recognizing color bars on double-sided color prints that is capable of facilitating the print quality control operation by the operator, as well as a color print quality control system and a color print quality evaluation apparatus that carry out this method.
Specifically, it is an object of the present invention to provide a method of recognizing color bars on double-sided color prints that is capable of controlling the print quality such as density for all the basic colors of a color print image on each side of a double-sided color print, facilitating the print quality control operation of a color print image on each side of the double-sided color print, and preventing the operator's misoperation in executing the print quality control so as to limit the occurrence of defective prints, as well as providing a color print quality control system and a color print quality evaluation apparatus that carry out this method.
It is another object of the present invention to provide a color print quality control system that is capable of omitting the necessity to provide such as a 180-degree turn switch in the color print quality evaluation apparatus conventionally required for sending the information that a print has been turned 180°, and hence reducing the workload of the operator to press the switch or the like.